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ntdll: Zero-initialize the syscall_frame used for starting threads on ARM/ARM64. 

This fixes an inconsistency since
fed7e7a78b (ntdll: Simulate a syscall
return when starting a thread); in that commit, on i386 and
x86_64, the syscall_frame used for starting the thread was
zeroed with a memset, while it wasn't on arm and arm64.

This had a noticable effect on float maths, where the
uninitialized frame->restore_flags field could have the
CONTEXT_FLOATING_POINT bit set. (call_init_thunk only ORs in
CONTEXT_INTEGER into the restore_flags field, on all architectures).
If that bit was set, it would restore uninitialized data into the
fpscr register, possibly setting the FPU in a nondefault rounding
mode.

Signed-off-by: Martin Storsjö <martin@martin.st>
Signed-off-by: Alexandre Julliard <julliard@winehq.org>
This commit is contained in:
Martin Storsjö 2022-03-04 18:15:56 +02:00 committed by Alexandre Julliard
parent 9b9d818252
commit 482b6a6dea
2 changed files with 2 additions and 0 deletions
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1
dlls/ntdll/unix/signal_arm.c
View File

@ -1105,6 +1105,7 @@ void DECLSPEC_HIDDEN call_init_thunk( LPTHREAD_START_ROUTINE entry, void *arg, B
ctx = (CONTEXT *)((ULONG_PTR)context.Sp & ~15) - 1;
*ctx = context;
ctx->ContextFlags = CONTEXT_FULL;
memset( frame, 0, sizeof(*frame) );
NtSetContextThread( GetCurrentThread(), ctx );
frame->sp = (DWORD)ctx;

1
dlls/ntdll/unix/signal_arm64.c
View File

@ -1202,6 +1202,7 @@ void DECLSPEC_HIDDEN call_init_thunk( LPTHREAD_START_ROUTINE entry, void *arg, B
ctx = (CONTEXT *)((ULONG_PTR)context.Sp & ~15) - 1;
*ctx = context;
ctx->ContextFlags = CONTEXT_FULL;
memset( frame, 0, sizeof(*frame) );
NtSetContextThread( GetCurrentThread(), ctx );
frame->sp = (ULONG64)ctx;